Why aren't my base styles updating in the preview?
If you're removing styling from a base style, those styles still apply until you have saved the base style.
Acquia Cohesion renames to Site Studio from version 6.2. Tell me more.
Base styles are CSS styles for HTML elements.
Yes, the component link field supports both internal and external URLs.
No, the entity browser does not work for component defaults as the entities are content, not config.
No site specific data is stored on the API.
The Youtube video embed is responsive so it should expand to the width of its parent. If you do need to set a width you can apply the Width CSS property through the Style Builder.